Add preview tabs (#9125)

This PR implements the preview tabs feature from VSCode.
More details and thanks for the head start of the implementation here
#6782.

Here is what I have observed from using the vscode implementation ([x]
-> already implemented):
- [x] Single click on project file opens tab as preview
- [x] Double click on item in project panel opens tab as permanent
- [x] Double click on the tab makes it permanent
- [x] Navigating away from the tab makes the tab permanent and the new
tab is shown as preview (e.g. GoToReference)
- [x] Existing preview tab is reused when opening a new tab
- [x] Dragging tab to the same/another panel makes the tab permanent
- [x] Opening a tab from the file finder makes the tab permanent
- [x] Editing a preview tab will make the tab permanent
- [x] Using the space key in the project panel opens the tab as preview
- [x] Handle navigation history correctly (restore a preview tab as
preview as well)
- [x] Restore preview tabs after restarting
- [x] Support opening files from file finder in preview mode (vscode:
"Enable Preview From Quick Open")
 
I need to do some more testing of the vscode implementation, there might
be other behaviors/workflows which im not aware of that open an item as
preview/make them permanent.

Showcase:


https://github.com/zed-industries/zed/assets/53836821/9be16515-c740-4905-bea1-88871112ef86


TODOs
- [x] Provide `enable_preview_tabs` setting
- [x] Write some tests
- [x] How should we handle this in collaboration mode (have not tested
the behavior so far)
- [x] Keyboard driven usage (probably need workspace commands)
- [x] Register `TogglePreviewTab` only when setting enabled?
- [x] Render preview tabs in tab switcher as italic
- [x] Render preview tabs in image viewer as italic
- [x] Should this be enabled by default (it is the default behavior in
VSCode)?
- [x] Docs

Future improvements (out of scope for now):
- Support preview mode for find all references and possibly other
multibuffers (VSCode: "Enable Preview From Code Navigation")


Release Notes:

- Added preview tabs
([#4922](https://github.com/zed-industries/zed/issues/4922)).

---------

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

crates/diagnostics/src/diagnostics.rs

@@ -38,7 +38,7 @@ pub use toolbar_controls::ToolbarControls;
 use ui::{h_flex, prelude::*, Icon, IconName, Label};
 use util::TryFutureExt;
 use workspace::{
-    item::{BreadcrumbText, Item, ItemEvent, ItemHandle},
+    item::{BreadcrumbText, Item, ItemEvent, ItemHandle, TabContentParams},
     ItemNavHistory, Pane, ToolbarItemLocation, Workspace,
 };
 
@@ -645,10 +645,10 @@ impl Item for ProjectDiagnosticsEditor {
         Some("Project Diagnostics".into())
     }
 
-    fn tab_content(&self, _detail: Option<usize>, selected: bool, _: &WindowContext) -> AnyElement {
+    fn tab_content(&self, params: TabContentParams, _: &WindowContext) -> AnyElement {
         if self.summary.error_count == 0 && self.summary.warning_count == 0 {
             Label::new("No problems")
-                .color(if selected {
+                .color(if params.selected {
                     Color::Default
                 } else {
                     Color::Muted
@@ -663,7 +663,7 @@ impl Item for ProjectDiagnosticsEditor {
                             .gap_1()
                             .child(Icon::new(IconName::XCircle).color(Color::Error))
                             .child(Label::new(self.summary.error_count.to_string()).color(
-                                if selected {
+                                if params.selected {
                                     Color::Default
                                 } else {
                                     Color::Muted
@@ -677,7 +677,7 @@ impl Item for ProjectDiagnosticsEditor {
                             .gap_1()
                             .child(Icon::new(IconName::ExclamationTriangle).color(Color::Warning))
                             .child(Label::new(self.summary.warning_count.to_string()).color(
-                                if selected {
+                                if params.selected {
                                     Color::Default
                                 } else {
                                     Color::Muted